Update mermaid version

[barrypress]

In a page I've written, I found that I needed to update the HTML framing mermaid content from

import mermaid from 'https://cdn.jsdelivr.net/npm/mermaid@10/dist/mermaid.esm.min.mjs';

to

import mermaid from 'https://cdn.jsdelivr.net/npm/mermaid@11/dist/mermaid.esm.min.mjs';

(i.e., bump the version) in order to get things like namespace in class diagrams to work. MacDown seems to need a similar update.